1. Field of the Invention
The present invention relates to a magnetic tape drive in which, when a power failure is detected in a fast-forwarding state or a rewinding state, a reel table is transferred from a non-brake state to a brake state.
2. Related Art
When a power failure occurs during a process of fast-forwarding or rewinding a magnetic tape, the magnetic tape slackens. Conventionally, as a countermeasure against such a situation, a technique is proposed in the Unexamined Japanese Utility Model Application Publication No. Hei2-26136. In the proposed technique, remaining amount detecting means for detecting the remaining amount of a loaded magnetic tape is disposed, and also power failure detecting means for detecting a failure of a supplied power and outputting a power failure detection signal is disposed. Furthermore, storage means for receiving the power failure detection signal, and for storing the tape remaining amount at a timing when the power failure detection signal is generated, as a power-failure tape remaining amount is disposed. When the power failure is then eliminated, the magnetic tape is rewound in one direction by a predetermined amount, and thereafter caused to run in the other direction. The tape remaining amount which is detected at this time is compared with the tape remaining amount at the stop. If the amounts coincide with each other, the running of the magnetic tape is stopped. After the power failure is eliminated, therefore, the magnetic tape is returned to the state where there is no slackening.
When the above-mentioned configuration is used, there arises the following problem. In the case where the fast-forwarding or rewinding operation is performed at a high speed in order to shorten the time period required for the operation, when a power failure occurs during the fast-forwarding or rewinding operation, the magnetic tape slackens in a larger amount. When the magnetic tape is then caused to run in the slackened state, therefore, the magnetic tape is easily tangled with a guide pin disposed in the running path, or twisted, thereby producing a fear that the magnetic tape may be broken.
The invention has been conducted in order to solve the problem. It is an object of the invention to provide a magnetic tape drive in which, when a power failure is detected in a fast-forwarding state or a rewinding state, the state of a reel table is transferred by using an remaining electric power from a non-brake state to a brake state, whereby, even when the power failure occurs in the fast-forwarding state or the rewinding state, a magnetic tape can be prevented from slackening.
It is another object of the invention to provide a magnetic tape drive in which, when a switching circuit is in an on state, a power failure is detected on the basis of a voltage appearing in a secondary coil to enable the power failure to be detected at an earlier timing, whereby the remaining electric power for transferring the state of a reel table from a non-brake state to a brake state can be sufficiently ensured.
It is a further object of the invention to provide a magnetic tape drive in which a power failure detecting section that transmits a second power failure detection signal at a timing which is later than a timing when a first power failure detection signal instructing the transfer of a reel table from a non-brake state to a brake state is disposed, and, even in the case where the first power failure detection signal is transmitted, when the second power failure detection signal is not transmitted, a normal mode is continued, whereby, also when the time period of an instantaneous power failure is relatively long, the mode is prevented from being transferred to a sleep mode.
In order to solve the problem, the invention is applied to a magnetic tape drive comprising a brake mechanism section which can transfer a state of a reel table from a non-brake state to a brake state by using an electric power that remains after a start of a power failure of a commercial power source, wherein the magnetic tape drive further comprises: a first power failure detecting section which, when a power failure of the commercial power source is detected, transmits a first power failure detection signal; and a controlling section which, when the first power failure detection signal is transmitted in a fast-forwarding state or a rewinding state, transfers the non-brake state of the brake mechanism section to the brake state.
When a power failure occurs in a fast-forwarding state or a rewinding state, the state of the brake mechanism section is transferred from the non-brake state to the brake state.
In addition to the above configuration, the invention is applied to a magnetic tape drive wherein the magnetic tape drive further comprises a switching power source which, when a switching circuit for switching a current flowing through a primary coil of a transformer is in an off state, takes out an output from a secondary coil of the transformer, and the first power failure detecting section transmits the first power failure detection signal on the basis of a voltage of the secondary coil of the transformer when the switching circuit is in an on state.
On the basis of the voltage of the secondary coil of the transformer when the switching circuit is in an on state, a power failure can be detected before the DC output voltage of the switching power source is lowered. In other words, the first power failure detection signal can be transmitted at a time when a large electric power remains in the switching power source.
In addition to the above configuration, the invention is applied to a magnetic tape drive wherein the controlling section is configured by a microcomputer having a normal mode, and a sleep mode which consumes a less power than the normal mode, the magnetic tape drive further comprises a second power failure detecting section which, when a power failure occurs, transmits a second power failure detection signal at a timing which is later than a timing when the first power failure detecting section transmits the first power failure detection signal, and also in a case where the first power failure detection signal is transmitted, the controlling section continues the normal modes when the second power failure detection signal is not transmitted, and is transferred from the normal mode to the sleep mode when the second power failure detection signal is transmitted.
When a power failure is eliminated during a period from the transmission of the first power failure detection signal to that of the second power failure detection signal, the transfer to the sleep mode is not performed.